Vehicle control device

ABSTRACT

A vehicle control device includes an information acquirer that acquires information on driving conditions of a vehicle at least containing a steering angle and a vehicle speed, a distribution amount setter that sets a distribution amount of a brake force to each of multiple wheels provided in the vehicle based on the driving conditions of the vehicle; and a brake controller that performs brake control of each of the multiple wheels according to the distribution amount set by the distribution amount setter. The distribution amount setter sets the distribution amount to zero when the steering angle SA is less than a first steering angle threshold where the steering angle SA is recognizable as a substantially neutral state.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a vehicle control device that performsbrake control of each of multiple wheels provided in a vehicle.

2. Description of the Related Art

Patent Literature 1 discloses the invention of a vehicle control devicethat performs brake control of each of multiple wheels provided in avehicle.

The vehicle control device according to Patent Literature 1 includes asteering sensor that detects a steering direction of a steering wheel, abraking device that performs a braking operation for each of themultiple wheels independently, and a brake force controller thatgenerates a brake force on a turning-inner wheel (specific wheel) on arear side in a vehicle traveling direction based on the travelingdirection detected by a vehicle speed sensor and a steering directiondetected by the steering sensor.

The vehicle control device according to Patent Literature 1 executestight-turn facilitation control of a specific wheel in order tofacilitate a tight turn of the vehicle, thereby making it possible toenhance the tight-turn performance with a simple configuration.

PRIOR ART DOCUMENT(S) Patent Literature(s)

Patent literature 1: JPH11-049020A

SUMMARY OF THE INVENTION

However, when the vehicle control device in the related art applies abrake force to a specific wheel at a timing when the specific wheelstarts to move in order to facilitate a tight turn of the vehicle, abrake system of the specific wheel may generate unusual sound (creepingnoise). Since such creeping noise is unpleasant unusual sound, there isa problem that the noise gives an unpleasant feeling to a passenger.

The present invention was made in view of the above circumstances, andhas an object to provide a vehicle control device capable of, evenduring execution of tight-turn facilitation control of a specific wheelin order to facilitate a tight turn of a vehicle, minimizing creepingnoise as much as possible to create a comfort driving environment,thereby contributing to a development of a sustainable transport system.

To achieve the above object, a vehicle control device according to thepresent invention includes: an information acquirer that acquiresinformation on driving conditions of a vehicle at least containing asteering angle of a steering wheel and a vehicle speed; a distributionamount setter that sets a distribution amount of a brake force to eachof a plurality of wheels provided in the vehicle based on the drivingconditions of the vehicle; and a brake controller that performs brakecontrol of each of the plurality of wheels according to the distributionamount set by the distribution amount setter, and has a most importantfeather in which when the steering angle is less than a first steeringangle threshold where the steering angle is recognizable as asubstantially neutral state, the distribution amount setter sets thedistribution amount to zero.

Even during execution of tight-turn facilitation control of a specificwheel in order to facilitate a tight turn of a vehicle, the vehiclecontrol device according to the present invention is capable ofminimizing creeping noise as much as possible to create a comfortdriving environment, thereby contributing to a development of asustainable transport system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an outline of the vehicle controldevice and its peripheral components according to an embodiment of thepresent invention.

FIG. 2A is a block diagram showing main components of a vehicle controldevice according to a first embodiment.

FIG. 2B is a characteristic chart that the vehicle control deviceaccording to the first embodiment refers to when setting a deadband fora steering angle, the characteristic chart presenting steering angles incomparison before and after deadband processing for the steering angle.

FIG. 2C is a characteristic chart of a first vehicle speed ratio thatthe vehicle control device according to the first embodiment refers towhen changing a deadband for the steering angle according to a change ina vehicle speed when the vehicle speed is within a low vehicle speedrange.

FIG. 2D is a characteristic chart of a second vehicle speed ratio thatthe vehicle control device according to the first embodiment refers towhen changing a brake force for a specific wheel according to a changein the vehicle speed when the vehicle speed is within a low vehiclespeed range.

FIG. 3 is a flowchart showing operations of the vehicle control deviceaccording to the first embodiment.

FIG. 4A is a block diagram showing main components of a vehicle controldevice according to a second embodiment.

FIG. 4B is a characteristic chart of a collision avoidance ratio thatthe vehicle control device according to the second embodiment refers towhen changing a brake force for a specific wheel according to a changein an obstacle separation distance.

FIG. 5 is a flowchart showing operations of the vehicle control deviceaccording to the second embodiment.

FIG. 6A is a diagram for explaining an operation for vehicle forwarddriving in the vehicle control device according to the secondembodiment.

FIG. 6B is a diagram for explaining an operation for vehicle backwarddriving in the vehicle control device according to the secondembodiment.

FIG. 7A is a diagram for explaining an operation for vehicle forwarddriving in the vehicle control device according to the secondembodiment.

FIG. 7B is a diagram for explaining an operation for vehicle backwarddriving in the vehicle control device according to the secondembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, vehicle control devices according to several embodiments ofthe present invention will be described in detail with reference to thedrawings as needed.

In the drawings to be described below, components having a commonfunction or equivalent function will be denoted with a common referencesign in principle. For convenience of explanation, the size and shape ofa characteristic chart are depicted schematically by deformation orexaggeration in some cases.

Outline of Vehicle Control Device 11 According to Embodiment ofInvention

A vehicle control device 11 according to an embodiment of the presentinvention will be described with reference to FIG. 1 . FIG. 1 is a blockdiagram showing an outline of the vehicle control device 11 and itsperipheral components according to the embodiment of the presentinvention.

As shown in FIG. 1 , the vehicle control device 11 is configured suchthat an integrated electronic control unit (ECU) 13, an input system 15,and an output system 17 are connected to each other via a communicationmedium 19 such as a control area network (CAN) so that information canbe exchanged with each other.

The integrated ECU 13 is composed of a microcomputer including a centralprocessing unit (CPU), a read only memory (ROM), a random access memory(RAM), and so on. This microcomputer reads and executes programs andinformation stored in the ROM, and thereby operates to perform executioncontrol of various functions which are equipped in the integrated ECU 13and which includes specific wheel brake control aiming to facilitate atight turn of a vehicle 10.

The integrated ECU 13 has a function to execute the specific wheel brakecontrol mainly aiming to facilitate a tight turn of the vehicle 10. Theinternal configuration of the integrated ECU 13 will be described indetail later.

As shown in FIG. 1 , as the input system 15, obstacle sensors 21, sidemonitoring cameras 23, a vehicle speed sensor 25, wheel speed sensors27, a steering angle sensor 29, a brake pedal sensor 31, an acceleratorpedal sensor 33, and a shift switch 35 are connected to thecommunication medium 19.

The obstacle sensors 21 have a function to obtain information on adistribution of objects existing around the vehicle 10 (hereinafterreferred to as “obstacles”). Although the obstacle OB (for example, seeFIGS. 6A and 6B and so on) is not particularly limited, the obstacle OBinclude columnar objects such as utility poles and traffic signs,structures such as block walls and guardrails, other vehicles, and soon. The information on the distribution of obstacles containsinformation on a positional relationship of each obstacle OB relative tothe vehicle 10 and a separation distance BD between the vehicle 10 andthe obstacle OB.

Although obstacle sensors 21 are not particularly limited, the obstaclesensors 21 are composed of sonar sensors, and so on, and installed atfour corners of the vehicle 10.

The information on the distribution of obstacles OB existing around thevehicle 10 obtained by the obstacle sensors 21 is transmitted to theintegrated ECU 13.

The side monitoring cameras 23 are installed at respective side mirrors(not shown) and have a function to capture images on the right and leftsides of the vehicle 10.

The images on the right and left sides of the vehicle 10 captured by theside monitoring cameras 23 are transmitted to the integrated ECU 13.

The vehicle speed sensor 25 has a function to detect a vehicle speed asa driving speed of the vehicle 10. The vehicle speed sensor 25 isattached to a crankshaft or a transmission of an internal combustionengine 45 and outputs a vehicle speed signal proportional to a rotationspeed of a driving shaft.

The information on the vehicle speed detected by the vehicle speedsensor 25 is transmitted to all of the integrated ECU 13, a BRK-ECU 37,and an ENG-ECU 39 via the communication medium 19.

The wheel speed sensors 27 have a function to detect respective wheelspeeds that are the rotation speeds of the multiple wheels provided inthe vehicle 10. The wheel speed sensor 27 is attached to, for example,the vicinity of a rotor provided to each of the multiple wheels andoutputs a wheel speed signal proportional to the rotation speed of therotor.

The information on the wheel speeds detected by the wheel speed sensors27 is transmitted to all of the integrated ECU 13, the BRK-ECU 37, andthe ENG-ECU 39 via the communication medium 19.

The steering angle sensor 29 has a function to detect information on asteering angle that is a rotation position of a steering wheel (notshown). The information on the steering angle is expressed, for example,by assigning a numerical value [0] to a neutral position of the steeringwheel, a numerical value with a positive sign to a right steering angle,and a numerical value with a negative sign to a left steering angle.

In other words, the information on the steering angle contains steeringdirection information expressed by the sign type (plus/minus) andsteering degree information expressed by the magnitude of the numericalvalue. In the process of information processing, the steering directioninformation (the sign type) and the steering degree information (theabsolute value of the steering angle) in the information on the steeringangle are individually handled.

The steering angle sensor 29 is attached to, for example, a steeringcolumn, and outputs a steering angle signal (the information on thesteering angle) depending on a rotation position of a steering shaft.

The information on the steering angle detected by the steering anglesensor 29 is transmitted to all of the integrated ECU 13, the BRK-ECU37, and the ENG-ECU 39 via the communication medium 19.

The brake pedal sensor 31 has a function to detect a pressing operationamount and a pressing operation torque (BP operation information) of abrake pedal (not shown) operated for braking the vehicle 10 from aninitial position (an operation position in a state where the driver'spressing operation is released).

The BP operation information detected by the brake pedal sensor 31 istransmitted to all of the integrated ECU 13, the BRK-ECU 37, and theENG-ECU 39 via the communication medium 19.

The accelerator pedal sensor 33 has a function to detect a pressingoperation amount (AP position information) of an accelerator pedal (notshown) operated for accelerating or decelerating the vehicle 10 from aninitial position (an operation position in a state where the driver'spressing operation is released).

The AP position information detected by the accelerator pedal sensor 33is transmitted to all of the integrated ECU 13, the BRK-ECU 37, and theENG-ECU 39 via the communication medium 19.

The shift switch 35 has a function to receive a driver's selectionoperation of a shift range (for example, such as D range, R range, Nrange, and P range). The shift switch 35 is provided near the driver'sseat in the vehicle 10.

Shift range operation information received by the shift switch 35 istransmitted to all of the integrated ECU 13, the BRK-ECU 37, and theENG-ECU 39 via the communication medium 19.

Meanwhile, as the output system 17, the BRK-ECU 37 and the ENG-ECU 39are connected to the communication medium 19 as shown in FIG. 1 .

The BRK-ECU 37 has a function to operate a motor cylinder device (see,for example, JP2015-110378A) by driving a brake motor 41 according to alevel of braking hydraulic pressure (primary hydraulic pressure)generated in a master cylinder (not shown) in response to a driver'sbraking operation, and thereby generate braking hydraulic pressure(secondary hydraulic pressure) for braking the vehicle 10.

For example, the BRK-ECU 37 also has a function to, in response to adeceleration control command transmitted from a brake controller 57belonging to the integrated ECU 13, drive a pressure pump (not shown) byusing a pump motor 43 and thereby perform control to adjust the brakeforce for each of the multiple (four) wheels to a brake force dependingon a target hydraulic pressure of the wheel.

The ENG-ECU 39 has a function to perform drive control of the internalcombustion engine 45 based on information on a driver's accelerationoperation (accelerator pedal press amount) obtained via the acceleratorpedal sensor 33.

In more detail, the ENG-ECU 39 performs the drive control of theinternal combustion engine 45 by controlling operations of a throttlevalve (not shown) for adjusting the intake air amount of the internalcombustion engine 45, an injector (not shown) for injecting the fuelgas, an ignition plug (not shown) for igniting the fuel, and so on.

Internal Configuration of Integrated ECU 13

Next, the internal configuration of the integrated ECU 13 will bedescribed with reference to FIG. 1 as needed.

FIG. 1 includes a functional block diagram representing the internalconfiguration of the integrated ECU 13.

As shown in FIG. 1 , the integrated ECU 13 includes an informationacquirer 51, a target wheel determiner 53, a distribution amount setter55, and the brake controller 57.

The information acquirer 51 has a function to acquire each of theinformation on the distribution of obstacles existing around the vehicle10 obtained by the obstacle sensors 21, the information of the images onthe right and left sides of the vehicle 10 captured by the sidemonitoring cameras 23, the information on the vehicle speed detected bythe vehicle speed sensor 25, the information on the wheel speedsdetected by the wheel speed sensors 27, the BP operation informationdetected by the brake pedal sensor 31, the AP position informationdetected by the accelerator pedal sensor 33, and the shift rangeoperation information received by the shift switch 35.

The target wheel determiner 53 has a function to determine a targetwheel to be involved in tight-turn facilitation control aiming tofacilitate a tight turn of the vehicle 10 based on the information onthe vehicle speed, the information on the wheel speeds, the informationon the steering angle, and so on acquired by the information acquirer51. In general, in the vehicle 10 that is turning while driving forwardat a slow vehicle speed (a vehicle speed of about 10 km/h or lower atwhich the vehicle 10 can stop quickly), the rear turning-inner wheel isselected as the specific wheel.

The distribution amount setter 55 plays roles in calculating anintegrated brake force IBF for the tight-turn facilitation controlaiming to facilitate a tight turn of the vehicle 10 based on theinformation on the vehicle speed VS, the information on the wheel speedsWS, the information on the steering angle SA, a required brake force BFbased on the BP operation information, and so on acquired by theinformation acquirer 51 and in setting a distribution amount of thecalculated integrated brake force IBF to each of the multiple wheelsincluding the specific wheel.

Various functions equipped in the distribution amount setter 55 will bedescribed in detail later.

The brake controller 57 preforms brake control for each of the wheelsincluding the specific wheel according to the distribution amounts setby the distribution amount setter 55. Note that, the brake controller 57executes the tight-turn facilitation control even in the absence ofinput of the BP operation information (the information on the requiredbrake force BF).

Block Configuration Showing Main Components of Vehicle Control Device11A According to First Embodiment of Invention

Next, main components of a vehicle control device 11A according to afirst embodiment of the present invention will be described withreference to FIGS. 2A to 2D as needed.

FIG. 2A is a block diagram showing the main components of the vehiclecontrol device 11A according to the first embodiment. FIG. 2B is acharacteristic chart which the vehicle control device 11A according tothe first embodiment refers to when setting a deadband for a steeringangle SA, and in which steering angles before and after deadbandprocessing for the steering angle SA are shown in comparison. FIG. 2C isa characteristic chart of a first vehicle speed ratio Rvs1 that thevehicle control device 11A according to the first embodiment refers towhen changing the deadband for the steering angle SA according to achange in the vehicle speed VS when the vehicle speed VS is within a lowvehicle speed range. FIG. 2D is a characteristic chart of a secondvehicle speed ratio Rvs2 that the vehicle control device 11A accordingto the first embodiment refers to when changing the brake force for aspecific wheel according to a change in the vehicle speed VS when thevehicle speed VS is within a low vehicle speed range.

As shown in FIG. 2A, the vehicle control device 11A according to thefirst embodiment includes a steering direction determiner 71, a steeringangle deadband setter 73, a steering angle command value calculator 74,a first vehicle speed ratio setter 75, a second vehicle speed ratiosetter 77, a first multiplier 80, a target wheel determiner 81, and abrake force distributor 83.

The steering direction determiner 71 determines a steering directionbased on the steering direction information (sign type) in theinformation on the steering angle SA.

As shown in FIG. 2B, the steering angle deadband setter 73 sets adeadband width for the steering angle SA based on the information on thesteering angle SA. The deadband width for the steering angle SA means anoperation region where steering is recognized as invalid based on theneutral position (steering center point) of the steering wheel. In theexample shown in FIG. 2B, an x axis represents a steering angle SA0before the deadband processing and a y axis represents a steering angleSA1 after the deadband processing. As shown in FIG. 2B, a deadband width2SAth for the steering angle SA is defined by a left steering criticalvalue (−SAth) and a right steering critical value (+SAth) positioned onboth sides of the steering center point. The absolute value |SAth| ofeach of the left steering critical value (−SAth) and the right steeringcritical value (+SAth) is equivalent to a first steering anglethreshold.

In the example shown in FIG. 2B, the information on the steering angleSA is expressed by a combination of the sign indicating the steeringdirection and the numerical value indicating the steering degree.

In more detail, the steering angle deadband setter 73 sets the firststeering angle threshold (|SAth|) based on the information on thesteering angle SA and the information on the vehicle speed VS (the firstvehicle speed ratio Rvs1). specifically, when the vehicle speed iswithin a low vehicle speed range (for example, a slow vehicle speedrange of about 10 km/h or lower), the steering angle deadband setter 73variably sets the first steering angle threshold (|SAth|) to a smallervalue as the vehicle speed VS becomes lower. In other words, thedeadband width 2SAth for the steering angle SA is set to be narrower asthe vehicle speed VS becomes lower.

Thus, when the vehicle speed VS is within the low vehicle speed range,even a slight change in the steering angle SA is reflected in acalculate result of calculation of a brake force for the tight-turnfacilitation control.

The steering angle command value calculator 74 calculates a steeringangle command value based on the deadband width 2SAth for the steeringangle SA set by the steering angle deadband setter 73.

The first vehicle speed ratio setter 75 has a function to set a value ofthe first vehicle speed ratio Rvs1 to be referred to for changing thedeadband width 2SAth for the steering angle SA according to a change inthe vehicle speed VS.

To implement the above function, when the vehicle speed VS is within thelow vehicle speed range (VS<VSth12), in particular, the first vehiclespeed ratio setter 75 appropriately sets a value less than 1 as thefirst vehicle speed ratio Rvs1 suitable for the vehicle speed VSaccording to the characteristic chart shown in FIG. 2C.

In more detail, in the first vehicle speed ratio Rvs1 having thecharacteristic shown in FIG. 2C, a fixed value (0) is allocated for thevehicle speed VS within a region up to an 11th vehicle speed valueVsth11 (VS=<VSth11), a linear variable value (0.5-1) is allocated forthe vehicle speed VS within a region above the 11th vehicle speed valueVsth11 up to a 12th vehicle speed value Vsth12 (VSth11<VS=<VSth12), anda fixed value (1) is allocated for the vehicle speed VS within a regionabove the 12th vehicle speed value Vsth12 (VS>VSth12).

The steering angle deadband setter 73 multiplies the value of the firstvehicle speed ratio Rvs1 set by the first vehicle speed ratio setter 75by the numerical value of the steering angle SA indicating the steeringdegree. In this way, when the vehicle speed VS is within the low vehiclespeed range (VS<VSth12), the deadband width 2SAth for the steering angleSA can be changed according to a change in the vehicle speed VS.

The second vehicle speed ratio setter 77 has a function to set a valueof the second vehicle speed ratio Rvs2 to be referred to for changingthe brake force for the specific wheel according to a change in thevehicle speed VS.

To implement the above function, when the vehicle speed VS is within alow vehicle speed range (VS=<VSth22), the second vehicle speed ratiosetter 77 appropriately sets a value less than 1 as the second vehiclespeed ratio Rvs2 suitable for the vehicle speed VS according to thecharacteristic chart shown in FIG. 2D.

In more detail, in the second vehicle speed ratio Rvs2 having thecharacteristic shown in FIG. 2D, a fixed value (0) is allocated for thevehicle speed VS within a region up to a 21st vehicle speed value VSth21(VS =<VSth21), and a variable value (0-1) having a gradually increasinglinear characteristic is allocated for the vehicle speed VS within aregion above the 21st vehicle speed value VSth21 up to a 22nd vehiclespeed value VSth22 (VSth21<VS=<VSth22).

Instead of the variable value (0-1) having the gradually increasinglinear characteristic, for example, a variable value (0-1) having agradually increasing non-linear characteristic with gentle rise from 0may be employed.

Then, a fixed value (1) is allocated for the vehicle speed VS within aregion above the 22nd vehicle speed value VSth22 up to a 23rd vehiclespeed value VSth23 (VSth22<VS=<VSth23). Further, a variable value (1-0)having a gradually decreasing linear characteristic is allocated for thevehicle speed VS within a region above the 23rd vehicle speed valueVSth23 up to a 24th vehicle speed value VSth24 (VSth23<VS=<VSth24), anda fixed value (0) is allocated for the vehicle speed VS within a regionabove the 24th vehicle speed value VSth24 (VS>VSth24).

The first multiplier 80 multiplies the value of the second vehicle speedratio Rvs2 set by the second vehicle speed ratio setter 77 by thesteering angle command value calculated by the steering angle commandvalue calculator 74.

In this way, in a case where the vehicle speed VS takes a valueexceeding the deadband region (0=<VS=<VSth21) in the low vehicle speedrange (in sum, a case where the specific wheel that was stopped startsto move), it is possible to, according to a change in the vehicle speedVS, gradually increase the brake force for the specific wheel as thevehicle speed VS becomes higher (gradually decrease the brake force forthe specific wheel as the vehicle speed VS becomes lower), instead ofinstantaneously raising the brake force for the specific wheel (sharplyincreasing the value of the second vehicle speed ratio Rvs2 from 0 to1).

As a result, even during execution of the tight-turn facilitationcontrol of the specific wheel in order to facilitate a tight turn of thevehicle 10, it is possible to minimize creeping noise as much aspossible to create a comfort driving environment, thereby contributingto a development of a sustainable transport system.

Here, the 11th vehicle speed value VSth11 (see FIG. 2C) for the firstvehicle speed ratio setter 75 and the 21st vehicle speed value VSth21(see FIG. 2D) for the second vehicle speed ratio setter 77 may be acommon value or values different from each other.

Similarly, the 12th vehicle speed value VSth12 (see FIG. 2C) for thefirst vehicle speed ratio setter 75 and the 22nd vehicle speed valueVSth22 (see FIG. 2D) for the second vehicle speed ratio setter 77 may bea common value or values different from each other.

The first multiplier 80 multiplies the steering angle command valuecalculated by the steering angle command value calculator 74 by thevalue of the second vehicle speed ratio Rvs2 set by the second vehiclespeed ratio setter 77. Thus, the first multiplier 80 calculates theintegrated brake force IBF that is a brake force for the tight-turnfacilitation control with both of the steering angle SA and the vehiclespeed VS taken into consideration. The integrated brake force IBF, thatis, a multiplication result of the first multiplier 80 is transmitted toboth of the target wheel determiner 81 and the brake force distributor83.

As in the target wheel determiner 53, the target wheel determiner 81determines a target wheel to be involved in the tight-turn facilitationcontrol aiming to facilitate a tight turn of the vehicle 10 based on theinformation on the vehicle speed VS, the information on the wheel speedsWS, the information on the steering angle SA, and so on acquired by theinformation acquirer 51. The target wheel thus determined may be hereinreferred to as a specific wheel in some cases.

The brake force distributor 83 distributes the integrated brake forceIBF for the tight-turn facilitation control among the multiple wheelsincluding the specific wheel as appropriate based on the information onthe vehicle speed VS, the information on the wheel speeds WS, theinformation on the steering angle SA, the information on the requiredbrake force, and so on acquired by the information acquirer 51, andoutputs each of the brake forces thus distributed as a brake forcecommand value.

Operations of Vehicle Control Device 11A According to First Embodiment

Next, operations of the vehicle control device 11A according to thefirst embodiment will be described with reference to FIG. 3 .

FIG. 3 is a flowchart showing operations of the vehicle control device11A according to the first embodiment.

In step S11 shown in FIG. 3 , the information acquirer 51 in theintegrated ECU 13 acquires each of various kinds of informationcontaining the information on the vehicle speed VS, the information onthe wheel speeds WS, the information on the steering angle SA, the BPoperation information, the AP position information, the shift rangeoperation information, the information on an obstacle distribution OD,the information on images on the right and left sides of the vehicle 10.

In step S12, the first vehicle speed ratio setter 75 sets the value ofthe first vehicle speed ratio Rvs1 to be referred to for changing thedeadband width 2SAth for the steering angle SA according to a change inthe vehicle speed VS.

In step S13, the steering angle deadband setter 73 sets the firststeering angle threshold (|SAth|) based on the information on thesteering angle SA and the information on the vehicle speed VS (the firstvehicle speed ratio Rvs1). As a result, the deadband width 2SAth for thesteering angle SA is set.

In step S14, the steering angle command value calculator 74 calculatesthe steering angle command value based on the deadband width 2SAth forthe steering angle SA set by the steering angle deadband setter 73.

In step S15, the second vehicle speed ratio setter 77 sets the value ofthe second vehicle speed ratio Rvs2 to be referred to for changing thebrake force for the specific wheel according to a change in the vehiclespeed VS. When the vehicle speed VS is within the low vehicle speedrange, the second vehicle speed ratio Rvs2 to be variably set dependingon the vehicle speed VS is set to a value less than 1.

In step S16, the first multiplier 80 multiplies the steering anglecommand value calculated by the steering angle command value calculator74 by the value of the second vehicle speed ratio Rvs2 set by the secondvehicle speed ratio setter 77, thereby calculating the integrated brakeforce IBF for the tight-turn facilitation control with both of thesteering angle SA and the vehicle speed VS taken into consideration.

In step S17, the target wheel determiner 81 determines a target wheel tobe involved in the tight-turn facilitation control aiming to facilitatea tight turn of the vehicle 10 based on the information on the vehiclespeed VS, the information on the wheel speeds WS, the information on thesteering angle SA, and so on acquired by the information acquirer 51 asin the target wheel determiner 53.

In step S18, the brake force distributor 83 distributes the integratedbrake force IBF for the tight-turn facilitation control among themultiple wheels including the specific wheel as appropriate based on theinformation on the vehicle speed VS, the information on the wheel speedsWS, the information on the steering angle SA, the information on therequired brake force, and so on acquired by the information acquirer 51,and outputs each of the brake forces thus distributed as a brake forcecommand value.

Effects of Vehicle Control Device 11A According to First Embodiment

In the vehicle control device 11A according to the first embodiment,when the vehicle speed VS is equal to or lower than the 22nd vehiclespeed value VSth22 (see FIG. 2D: equivalent to the “first vehicle speedthreshold” of the present invention) within the low vehicle speed range(for example, the slow vehicle speed range of about 10 km/h or less),the distribution amount setter 55 sets a distribution amount of thebrake force to each of the multiple wheels including the specific wheelto a value which is smaller than a distribution amount when the vehiclespeed VS exceeds the 22nd vehicle speed value VSth22.

When the vehicle speed VS is equal to or lower than the 22nd vehiclespeed value VSth22 (the first vehicle speed threshold) and isincreasing, in particular, the distribution amount setter 55 graduallyincreases the distribution amount until the vehicle speed VS exceeds the22nd vehicle speed value VSth22 (see FIG. 2D).

In this way, in the case where the vehicle speed VS takes a valueexceeding a deadband region (0=<VS=<VSth21) in the low vehicle speedrange (in sum, the case where the specific wheel that was stopped startsto move), the vehicle control device 11A according to the firstembodiment is capable of gradually increasing the brake force for thespecific wheel as the vehicle speed VS becomes higher according to achange in the vehicle speed VS.

The vehicle control device 11A according to the first embodiment iscapable of, even during execution of the tight-turn facilitation controlof the specific wheel in order to facilitate a tight turn of the vehicle10, minimizing creeping noise as much as possible to create a comfortdriving environment, thereby contributing to a development of asustainable transport system.

Moreover, as shown in FIG. 2D, when the vehicle speed VS is equal to orlower than the 22nd vehicle speed value VSth22 (the first vehicle speedthreshold), the distribution amount setter 55 calculates thedistribution amounts based on the wheel speeds WS if the vehicle speedVS is equal to or lower than the 21st vehicle speed value VSth21 (thesecond vehicle speed threshold) that is lower than the 22nd vehiclespeed value VSth22, or calculates the distribution amounts based on thevehicle speed VS if the vehicle speed VS exceeds the 21st vehicle speedvalue VSth21 (the second vehicle speed threshold).

In the vehicle control device 11A according to the first embodiment,along with a change in the vehicle speed VS, the information as a basisfor calculating the distribution amounts is switched to use at least onekind of the vehicle speed VS and the wheel speeds WS.

When the vehicle speed VS is equal to or lower than the 21st vehiclespeed value VSth21 (the second vehicle speed threshold) lower than the22nd vehicle speed value VSth22 (the vehicle speed VS is very low), inparticular, the distribution amounts are calculated based on the wheelspeeds WS that enable the brake control of each of the multiple wheelsto be executed with high accuracy. This makes it possible to furtherenhance the effect of executing suitable tight-turn facilitation controlwhile minimizing creeping noise as much as possible.

In addition, the use of at least one kind of the vehicle speed VS andthe wheel speeds WS as the information as the basis for calculating thedistribution amounts can be expected to obtain an effect of enabling thetight-turn facilitation control to be executed as far as possible evenif a failure to acquire one kind of the vehicle speed VS and the wheelspeeds WS occurs.

In the vehicle control device 11A according to the first embodiment, thedistribution amount setter 55 may be configured to set the distributionamount to zero when the steering angle SA is less than the firststeering angle threshold (SA<|SAth|: see FIG. 2B) where the steeringangle SA is recognizable as a substantially neutral state. In this case,when the steering angle SA is less than the first steering anglethreshold, the distribution amount is zero. Here, the expression thatthe distribution amount is zero is a concept that includes both of amode were a previously non-zero value is changed to zero and a modewhere a previously zero value remains zero.

The distribution amount setter 55 sets the distribution amount to zero(consequently the distribution amount is zero) when the steering angleSA is less than the first steering angle threshold where the steeringangle SA is recognizable as the substantially neutral state. Thus, evenwhen slight correction steering, which may appear during straightdriving, is performed, the vehicle control device 11A according to thefirst embodiment invalidates the correction steering and is preventedfrom executing the tight-turn facilitation control. As a result, anunexpected execution of the tight-turn facilitation control can beavoided.

In addition, even during execution of the tight-turn facilitationcontrol on the specific wheel in order to facilitate a tight turn of thevehicle 10, it is possible to minimize creeping noise as much aspossible to create a comfort driving environment, thereby contributingto a development of a sustainable transport system.

Block Configuration Showing Main Components of Vehicle Control Device11B According to Second Embodiment of Invention

Next, main components of a vehicle control device 11B according to asecond embodiment of the present invention will be described withreference to FIGS. 4A to 4D as needed.

FIG. 4A is a block diagram showing the main components of the vehiclecontrol device 11B according to the second embodiment. FIG. 4B is acharacteristic chart of a collision avoidance ratio Rca that the vehiclecontrol device 11B according to the second embodiment refers to whenchanging a brake force for a specific wheel according to a change in anobstacle separation distance BD.

The vehicle control device 11A according to the first embodiment and thevehicle control device 11B according to the second embodiment have somecomponents in common.

Therefore, the description of the vehicle control device 11B accordingto the second embodiment will be given by focusing on differencesbetween the two while omitting the description of the components commonto the two.

As shown in FIG. 4A, the vehicle control device 11B according to thesecond embodiment includes a steering direction determiner 71, asteering angle deadband setter 73, a steering angle command valuecalculator 74, a first vehicle speed ratio setter 75, a second vehiclespeed ratio setter 77, a collision avoidance ratio setter 78, a secondmultiplier 79, a first multiplier 80, a target wheel determiner 81, anda brake force distributor 83.

Here, as compared with the vehicle control device 11A according to thefirst embodiment, the collision avoidance ratio setter 78 and the secondmultiplier 79 are added to the vehicle control device 11B according tothe second embodiment.

The collision avoidance ratio setter 78 has a function to, when anobstacle OB exists around the vehicle 10, set a collision avoidanceratio Rca to be referred to for changing a brake force for a specificwheel according to a change in an obstacle separation distance BD thatis a distance between the vehicle 10 and the obstacle OB.

To implement the above function, when an obstacle OB exists around thevehicle 10, the collision avoidance ratio setter 78 sets the value ofthe collision avoidance ratio Rca as appropriate depending on a changein the obstacle separation distance BD according to the characteristicchart shown in FIG. 4B.

In more detail, in the collision avoidance ratio Rca having thecharacteristic shown in FIG. 4B, a fixed value (2) is allocated for theobstacle separation distance BD within a region up to a first separationdistance value BDth1 (BD=<BDth1), a variable value (2-1) having agradually decreasing linear characteristic is allocated for the obstacleseparation distance BD within a region above the first separationdistance value BDth1 up to a second separation distance value BDth2(BDth1<BD=<BDth2), and a fixed value (1) is allocated for the obstacleseparation distance BD within a region above the second separationdistance value BDth2 (BD>BDth2).

Although the above collision avoidance ratio Rca is described by takingthe example where the fixed value (2) is allocated for the obstacleseparation distance BD within the region up to the first separationdistance value BDth1, the present invention is not limited to thisexample. It is possible to employ a mode where a certain fixed value(which should be a value more than 1) is allocated for the obstacleseparation distance BD within the region up to the first separationdistance value BDth1.

In addition, in the above collision avoidance ratio Rca, a variablevalue (2-1) having a gradually decreasing non-linear characteristic maybe employed in place of the variable value (2-1) having the graduallydecreasing linear characteristic.

The second multiplier 79 multiplies the value of the collision avoidanceratio Rca set by the collision avoidance ratio setter 78 by the value ofthe second vehicle speed ratio Rvs2 set by the second vehicle speedratio setter 77. A correction coefficient CF that is the multiplicationresult of the second multiplier 79 is transmitted to the firstmultiplier 80.

Thus, in a case where the obstacle separation distance BD takes a valueequal to or less than the first separation distance value BDth1(BD=<BDth1) (in sum, a case where a risk of collision is relatively highwith a small obstacle separation distance BD), the value of thecollision avoidance ratio Rca is fixed to (2) (the amount of control isdoubled) irrespective of a change in the obstacle separation distanceBD, so that a collision can be avoided (the risk of collision can bereduced).

Meanwhile, in a case where the obstacle separation distance BD takes avalue more than the first separation distance value BDth1 and that isequal to or less than the second separation distance value BDth2(BDth1<BD=<BDth2) (in sum, a case where the risk of collision isrelatively low with a large obstacle separation distance BD, the amountof control is gradually decreased as the obstacle separation distance BDbecomes larger according to a change in the obstacle separation distanceBD, so that an influence of the collision avoidance (risk of collisionreduction) on the amount of control can be gradually decreased.

Then, in a case where the obstacle separation distance BD takes a valuemore than the second separation distance value BDth2 (BD>BDth2) (in sum,a case where the risk of collision is sufficiently low with asufficiently large obstacle separation distance BD), the value of thecollision avoidance ratio Rca is fixed to (1) irrespective of a changein the obstacle separation distance BD, so that the influence of thecollision avoidance (the reduction in the risk of collision) on theamount of control can be eliminated.

The first multiplier 80 multiplies the steering angle command valuecalculated by the steering angle command value calculator 74 by themultiplication result (the correction coefficient CF) of the secondmultiplier 79. Thus, the first multiplier 80 calculates the integratedbrake force IBF that is the brake force for the tight-turn facilitationcontrol with all of the steering angle SA, the vehicle speed VS, and theobstacle distribution OD taken into consideration. The integrated brakeforce IBF, that is, the multiplication result of the first multiplier 80is transmitted to both of the target wheel determiner 81 and the brakeforce distributor 83.

Operations of Vehicle Control Device 11B According to Second Embodiment

Next, operations of the vehicle control device 11B according to thesecond embodiment will be described with reference to FIG. 5 .

FIG. 5 is a flowchart showing operations of the vehicle control device11B according to the second embodiment.

The vehicle control device 11A according to the first embodiment and thevehicle control device 11B according to the second embodiment performsome operations in common.

Therefore, the description of the operations of the vehicle controldevice 11B according to the second embodiment will be given by focusingon differences between the two while omitting the description of theoperations common to the two.

In step S31 shown in FIG. 5 , when an obstacle OB exists around thevehicle 10, the collision avoidance ratio setter 78 sets the value ofthe collision avoidance ratio Rca to be referred to for changing thebrake force for the specific wheel according to a change in the obstacleseparation distance BD.

In the case where the obstacle separation distance BD takes a valueequal to or less than the first separation distance value BDth1(BD=<BDth1) (in sum, the case where the risk of collision is relativelyhigh with a small obstacle separation distance BD), the fixed value (2:the amount of control is doubled) is set as the collision avoidanceratio Rca irrespective of a change in the obstacle separation distanceBD. This makes it possible to avoid a collision (reduce the risk ofcollision) in the case where the risk of collision is relatively high.

In step S32, the second multiplier 79 multiplies the value of the secondvehicle speed ratio Rvs2 set by the second vehicle speed ratio setter 77by the value of the collision avoidance ratio Rca set by the collisionavoidance ratio setter 78, thereby calculating the correctioncoefficient CF with both of the vehicle speed VS and the obstacledistribution OD taken into consideration.

In step S33, the first multiplier 80 multiplies the steering anglecommand value calculated by the steering angle command value calculator74 by the multiplication result (correction coefficient CF) of thesecond multiplier 79, thereby calculating the integrated brake force IBFthat is the brake force for the tight-turn facilitation control with allof the steering angle SA, the vehicle speed VS, and the obstacledistribution OD taken into consideration.

Effects of Vehicle Control Device 11B According to Second Embodiment

Next, effects of the vehicle control device 11B according to the secondembodiment will be described with reference to FIGS. 6A, 6B, 7A, and 7Bas needed.

FIG. 6A is a diagram for explaining an operation for vehicle forwarddriving in the vehicle control device 11B according to the secondembodiment. FIG. 6B is a diagram for explaining an operation for vehiclebackward driving in the vehicle control device 11B according to thesecond embodiment. FIG. 7A is a diagram for explaining an operation forvehicle forward driving in the vehicle control device 11B according tothe second embodiment. FIG. 7B is a diagram for explaining an operationfor vehicle backward driving in the vehicle control device 11B accordingto the second embodiment.

In the vehicle control device 11B according to the second embodiment,the distribution amount setter 55 sets the distribution amount to zerowhen the steering angle SA is less than the first steering anglethreshold (SA<|SAth|: see FIG. 2B) where the steering angle SA isrecognizable as a substantially neutral state. In sum, when the steeringangle SA is less than the first steering angle threshold, thedistribution amount is zero. Here, the expression that the distributionamount is zero is a concept that includes both of a mode were apreviously non-zero value is changed to zero and a mode where apreviously zero value remains zero.

The distribution amount setter 55 sets the distribution amount to zero(consequently the distribution amount is zero) when the steering angleSA is less than the first steering angle threshold where the steeringangle SA is recognizable as the substantially neutral state. Thus, evenwhen slight correction steering, which may appear during straightdriving, is performed, the vehicle control device 11B according to thesecond embodiment invalidates the correction steering and is preventedfrom executing the tight-turn facilitation control. As a result, anunexpected execution of the tight-turn facilitation control can beavoided.

In addition, even during execution of the tight-turn facilitationcontrol of the specific wheel in order to facilitate a tight turn of thevehicle 10, it is possible to minimize creeping noise as much aspossible to create a comfort driving environment, thereby contributingto a development of a sustainable transport system.

In particular, when the vehicle speed VS is within the low vehicle speedrange, the first steering angle threshold (|SAth|) is variably set to asmaller value as the vehicle speed VS becomes lower (see FIG. 2C).

Thus, in a case where slight steering is performed under a relativelylow vehicle speed VS, the vehicle control device 11B according to thesecond embodiment can utilize the slight steering for the tight-turnfacilitation control, even though the presence of the slight steeringmay be ignored under a relatively high vehicle speed VS.

The vehicle control device 11B according to the second embodiment iscapable of executing the tight-turn facilitation control with thevehicle speed VS and the steering angle SA taken into consideration asappropriate, thereby minimizing creeping noise as much as possible tocreate a comfort driving environment, and thus contributing to adevelopment of a sustainable transport system.

Moreover, the distribution amount setter 55 sets the distributionamounts of the brake force to the respective multiple wheels provided inthe vehicle 10 based on the driving conditions of the vehicle 10 (thevehicle speed VS and the steering angle SA) and the obstacledistribution OD. In particular, when an obstacle OB exists around thevehicle 10, the distribution amount setter 55 sets the distributionamounts such that a collision with the obstacle OB can be avoided.

Since when an obstacle OB exists around the vehicle 10, the distributionamount setter 55 sets the distribution amounts such that a collisionwith the obstacle OB can be avoided, the vehicle control device 11Baccording to the second embodiment is capable of obtaining the effect ofavoiding a collision with the obstacle OB in addition to the effect ofexecuting the suitable tight-turn facilitation control while minimizingcreeping noise as much as possible.

In addition, when an obstacle OB exists around the vehicle 10, thedistribution amount setter 55 evaluates a risk of collision with theobstacle OB based on a turning direction of the vehicle 10, an existencedirection of the obstacle OB relative to the vehicle 10, the separationdistance BG between the vehicle 10 and the obstacle OB, and sets thedistribution amounts based on the evaluation result of the risk ofcollision such that the risk of collision can be reduced.

Since when an obstacle OB exists around the vehicle 10, the distributionamount setter 55 evaluates the risk of collision with the obstacle OBand sets the distribution amounts based on the evaluation result of therisk of collision such that the risk of collision can be reduced, thevehicle control device 11B according to the second embodiment is capableof further enhancing the effect of avoiding a collision with theobstacle OB in addition to the effect of executing the suitabletight-turn facilitation control while minimizing creeping noise as muchas possible.

Further, when an obstacle OB exists around the vehicle 10, as theseparation distance BD between the vehicle 10 and the obstacle OBbecomes smaller (see FIG. 4B), the distribution amount setter 55recognizes that the risk of collision is higher and sets the largerdistribution amounts such that the risk of collision can be reduced.

Since when an obstacle OB exists around the vehicle 10, as theseparation distance BD between the vehicle 10 and the obstacle OBbecomes smaller (see FIG. 4B), the distribution amount setter 55recognizes that the risk of collision is higher and sets the largerdistribution amounts such that the risk of collision can be reduced, thevehicle control device 11B according to the second embodiment is capableof further enhancing the effect of avoiding a collision with theobstacle OB in addition to the effect of executing the suitabletight-turn facilitation control while minimizing creeping noise as muchas possible.

Furthermore, as shown in Figs, 6A and 6B, when an obstacle OB exists onone side of the vehicle 10 and the one side of the vehicle 10 coincideswith the outer side in a turning direction of the vehicle 10 and if therisk of collision will be reduced with setting of the large distributionamounts for the inner wheels in the turning direction of the vehicle 10,the distribution amount setter 55 sets the large distribution amountsfor the inner wheels in the turning direction of the vehicle 10 suchthat the risk of collision can be reduced.

Since when an obstacle OB exists on one side of the vehicle 10 and theone side of the vehicle 10 coincides with the outer side in a turningdirection of the vehicle 10 and if the risk of collision will be reducedwith setting of the large distribution amounts for the inner wheels inthe turning direction of the vehicle 10, the distribution amount setter55 sets the large distribution amounts for the inner wheels in theturning direction of the vehicle 10 such that the risk of collision canbe reduced, the vehicle control device 11B according to the secondembodiment is capable of adequately obtaining the effect of avoiding acollision with the obstacle OB in addition to the effect of executingthe suitable tight-turn facilitation control while minimizing creepingnoise as much as possible.

Moreover, as shown in FIGS. 7A and 7B, when an obstacle OB exists on oneside of the vehicle 10 and the one side of the vehicle 10 coincides withthe inner side in a turning direction of the vehicle 10 and if the riskof collision will be increased with setting of the large distributionamounts for the inner wheels in the turning direction of the vehicle 10,the distribution amount setter 55 sets the large distribution amountsfor the outer wheels in the turning direction of the vehicle 10 suchthat the risk of collision can be reduced.

Since when an obstacle OB exists on one side of the vehicle 10 and theone side of the vehicle 10 coincides with the inner side in a turningdirection of the vehicle 10 and if the risk of collision will beincreased with setting of the large distribution amounts for the innerwheels in the turning direction of the vehicle 10, the distributionamount setter 55 sets the large distribution amounts for the outerwheels in the turning direction of the vehicle 10 such that the risk ofcollision can be reduced, the vehicle control device 11B according tothe second embodiment is capable of adequately obtaining the effect ofavoiding a collision with the obstacle OB in addition to the effect ofexecuting the suitable tight-turn facilitation control while minimizingcreeping noise as much as possible.

Other Embodiments

The several embodiments described above merely represent embodiedexamples of the present invention. Therefore, the technical scope of thepresent invention should not be interpreted by being limited to theseembodiments. The present invention may be carried out in various modeswithout departing from the gist or main features of the presentinvention.

For example, the embodiments of the present invention are described byusing the example in which the vehicle control device 11 according tothe embodiment of the present invention is applied to the vehicleequipped with the internal combustion engine as a power source, but thepresent invention is not limited to this example. The present inventionmay be applied to an electric vehicle equipped with a motor generator asa power source, a hybrid vehicle equipped with an internal combustionengine and a motor generator as power sources, and the like.

What is claimed is:
 1. A vehicle control device comprising: aninformation acquirer that acquires information on driving conditions ofa vehicle at least containing a steering angle of a steering wheel and avehicle speed; a distribution amount setter that sets a distributionamount of a brake force to each of a plurality of wheels provided in thevehicle based on the driving conditions of the vehicle; and a brakecontroller that performs brake control of each of the plurality ofwheels according to the distribution amount set by the distributionamount setter, wherein when the steering angle is less than a firststeering angle threshold where the steering angle is recognizable as asubstantially neutral state, the distribution amount setter sets thedistribution amount to zero.
 2. The vehicle control device according toclaim 1, wherein when the vehicle speed is within a low vehicle speedrange, the first steering angle threshold is variably set to a valuethat becomes smaller as the vehicle speed becomes lower.
 3. A vehiclecontrol device comprising: an information acquirer that acquiresinformation on driving conditions of a vehicle at least containing asteering angle of a steering wheel and a vehicle speed and informationon a distribution of an obstacle existing around the vehicle; adistribution amount setter that sets a distribution amount of a brakeforce to each of a plurality of wheels provided in the vehicle based onthe driving conditions of the vehicle and the distribution of theobstacle; and a brake controller that performs brake control of each ofthe plurality of wheels according to the distribution amount set by thedistribution amount setter, wherein when the obstacle exists around thevehicle, the distribution amount setter sets the larger distributionamount than when the obstacle does not exist around vehicle.
 4. Thevehicle control device according to claim 3, wherein when the obstacleexists around the vehicle, the distribution amount setter evaluates arisk of collision with the obstacle based on a turning direction of thevehicle, an existence direction of the obstacle, and a separationdistance between the vehicle and the obstacle, and sets the distributionamount based on an evaluation result of the risk of collision such thatthe risk of collision is reduced.
 5. The vehicle control deviceaccording to claim 3, wherein when the obstacle exists around thevehicle, the distribution amount setter sets the larger distributionamount as the separation distance between the vehicle and the obstaclebecomes smaller.
 6. The vehicle control device according to claim 3,wherein when the obstacle exists on one side of the vehicle and the oneside coincides with an outer side in a turning direction of the vehicle,the distribution amount setter sets the large distribution amounts forthe inner wheels in the turning direction of the vehicle.
 7. The vehiclecontrol device according to claim 3, wherein when the obstacle exists onone side of the vehicle and the one side coincides with an inner side ina turning direction of the vehicle, the distribution amount setter setsthe large distribution amounts for the outer wheels in the turningdirection of the vehicle.